Optoelectronic device and method of forming the same

ABSTRACT

An optoelectronic device including a substrate, a half-boat-shaped material layer, a deep trench isolation structure, and an optical waveguide is provided. The substrate has a first area. The half-boat-shaped material layer is disposed in the substrate within the first area. The refractive index of the half-boat-shaped material layer is lower than that of the substrate. A top surface of the half-boat-shaped material layer is coplanar with the surface of the substrate. The deep trench isolation structure is disposed in the substrate within the first area and located at one side of a bow portion of the half-boat-shaped material layer. The optical waveguide is disposed on the substrate within the first area. The optical waveguide overlaps a portion of the deep trench isolation structure and at least a portion of the half-boat-shaped material layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a semiconductor device and amethod of forming the same, and more particularly, to an optoelectronicdevice and a method of forming the same.

2. Description of Related Art

An optoelectronic device includes both optical devices and electronicdevices, wherein the optical devices include a coupler for receiving anoptical signal from an optical fiber and an optical waveguide forreceiving and transmitting the optical signal, and the electronicdevices include a metal-oxide-semiconductor (MOS) device for controllingthe optical waveguide. The MOS device controls the optical waveguide totransform the optical signal into an electronic signal so that theoptical signal can be used by other electronic devices.

Conventionally, the electronic devices (for example, the MOS device) areformed on a chip while the optical devices (for example, the coupler andthe optical waveguide) are formed on another chip, and the devices arethen connected with each other through conductive lines. However, anoptoelectronic device fabricated through such a technique takes up toomuch surface area and has a complicated system. Accordingly, how to formthe MOS device, the coupler, and the optical waveguide in a single chiphas become highly focused in the industry.

Presently, the technique of forming an optical waveguide on asilicon-on-insulator (SOI) substrate has become very mature. However, ifa MOS device is also formed on the SOI substrate, the modeling of theMOS device should be fine tuned again, which is time- andlabour-consuming and not economical. Thereby, a method of forming anoptical waveguide and a MOS device on a bulk-Si substrate is to bedeveloped.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an optoelectronicdevice, wherein an optical waveguide, a coupler, and ametal-oxide-semiconductor (MOS) device are effectively integrated into asingle chip.

The present invention is directed to a method of forming anoptoelectronic device, wherein an optical waveguide, a coupler, and aMOS device are formed on a bulk-Si substrate through the existingprocesses.

The present invention provides an optoelectronic device including asubstrate, a half-boat-shaped material layer, a deep trench isolationstructure, and an optical waveguide. The substrate has a first area. Thehalf-boat-shaped material layer is disposed in the substrate within thefirst area. The refractive index of the half-boat-shaped material layeris lower than that of the substrate. A top surface of thehalf-boat-shaped material layer is coplanar with the surface of thesubstrate. The deep trench isolation structure is disposed in thesubstrate within the first area and located at one side of a bow portionof the half-boat-shaped material layer. The optical waveguide isdisposed on the substrate within the first area. The optical waveguideoverlaps a portion of the deep trench isolation structure and at least aportion of the half-boat-shaped material layer.

According to an embodiment of the present invention, the substrateincludes a bulk-Si substrate.

According to an embodiment of the present invention, the material of thehalf-boat-shaped material layer includes SiO_(x).

According to an embodiment of the present invention, the material of theoptical waveguide includes polysilicon, amorphous silicon, or singlecrystal silicon.

According to an embodiment of the present invention, the depth of thedeep trench isolation structure is in micron level.

According to an embodiment of the present invention, the deep trenchisolation structure and the half-boat-shaped material layer are kept adistance apart or directly adjacent to each other.

According to an embodiment of the present invention, a laser is coupledto a stern portion of the half-boat-shaped material layer through anoptical fiber.

According to an embodiment of the present invention, the substratefurther includes a second area, and the first area and the second areaare separated from each other by a shallow trench isolation structure.

According to an embodiment of the present invention, the optoelectronicdevice further includes a MOS device disposed within the second area.

The present invention further provides a method of forming anoptoelectronic device. First, a substrate having a first area isprovided. Then, a half-boat-shaped material layer is formed within thefirst area, wherein the refractive index of the half-boat-shapedmaterial layer is lower than that of the substrate, and a top surface ofthe half-boat-shaped material layer is coplanar with the surface of thesubstrate. Thereafter, a deep trench isolation structure is formed inthe substrate within the first area, wherein the deep trench isolationstructure is formed at one side of a bow portion of the half-boat-shapedmaterial layer. Next, an optical waveguide is formed on the substratewithin the first area, wherein the optical waveguide overlaps a portionof the deep trench isolation structure and at least a portion of thehalf-boat-shaped material layer.

According to an embodiment of the present invention, the step of formingthe half-boat-shaped material layer includes performing a plurality ofion implantation processes on the substrate to form a plurality ofstep-shaped ion implanted regions in the substrate within the firstarea.

According to an embodiment of the present invention, each of the ionimplantation processes includes an O⁺ ion implantation process.

According to an embodiment of the present invention, the implantationdosage of each of the ion implantation processes is 10¹⁴-10²¹ atoms percubic centimeter.

According to an embodiment of the present invention, the step of formingthe half-boat-shaped material layer further includes performing anannealing process to diffuse the ion implanted regions, so as to formthe half-boat-shaped material layer.

According to an embodiment of the present invention, the substrateincludes a bulk-Si substrate.

According to an embodiment of the present invention, the material of theoptical waveguide includes polysilicon, amorphous silicon, or singlecrystal silicon.

According to an embodiment of the present invention, the depth of thedeep trench isolation structure is in micron level.

According to an embodiment of the present invention, the deep trenchisolation structure and the half-boat-shaped material layer are kept adistance apart or directly adjacent to each other.

According to an embodiment of the present invention, the substratefurther has a second area, and the first area and the second area areseparated from each other by a shallow trench isolation structure.

According to an embodiment of the present invention, the method offorming the optoelectronic device further includes forming a MOS devicewithin the second area.

According to an embodiment of the present invention, the gate of the MOSdevice is simultaneously formed during the step of forming the opticalwaveguide.

According to an embodiment of the present invention, the MOS device isformed after the optical waveguide is formed.

As described above, in an optoelectronic device provided by the presentinvention, an optical waveguide, a coupler, and a MOS device areeffectively integrated into a single chip so that less surface area istaken and the system is simplified. In addition, in the method offorming an optoelectronic device provided by the present invention, anoptical waveguide, a coupler, and a MOS device can be formed on abulk-Si substrate by using the existing semiconductor equipments.Thereby, a simple, easy and competitive technique is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a schematic cross-sectional view of an optoelectronic deviceaccording to an embodiment of the present invention.

FIG. 2 is a schematic three-dimensional view of a half-boat-shapedmaterial layer according to an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of an optoelectronic deviceaccording to another embodiment of the present invention.

FIG. 4 is a simplified schematic top view illustrating a packaging of anoptoelectronic device according to an embodiment of the presentinvention.

FIGS. 5A-5D are schematic cross-sectional views illustrating a method offorming an optoelectronic device according to a first embodiment of thepresent invention.

FIG. 6 is a schematic three-dimensional view illustrating ion implantedregions for forming a half-boat-shaped material layer according to anembodiment of the present invention.

FIGS. 7A-7C are schematic cross-sectional views illustrating a method offorming an optoelectronic device according to a second embodiment of thepresent invention.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

FIG. 1 is a schematic cross-sectional view of an optoelectronic deviceaccording to an embodiment of the present invention.

Referring to FIG. 1, the optoelectronic device 100 includes a substrate102, a half-boat-shaped material layer 106, a deep trench isolationstructure 108, and an optical waveguide 110. The substrate 102 may be abulk-Si substrate and has a first area 104 a and a second area 104 b.The first area 104 a is used for forming optical devices (for example,the optical waveguide 110 and a coupler 118), and the second area 104 bis used for forming electronic devices (for example, ametal-oxide-semiconductor (MOS) device 130). The first area 104 a andthe second area 104 b may be separated from each other by a shallowtrench isolation structure 101.

The half-boat-shaped material layer 106 is disposed in the substrate 102within the first area 104 a. FIG. 2 is a schematic three-dimensionalview of the half-boat-shaped material layer 106, wherein thehalf-boat-shaped material layer 106 in FIG. 1 is illustrated along thecross-section I-I′ and accordingly presents a L-shape. The refractiveindex of the half-boat-shaped material layer 106 is lower than that ofthe substrate 102. In an embodiment, the material of thehalf-boat-shaped material layer 106 includes SiO_(x), and thehalf-boat-shaped material layer 106 is formed through an O⁺ ionimplantation process. Further, the half-boat-shaped material layer 106can be formed through another ion implantation process, as long as therefractive index of the half-boat-shaped material layer 106 is lowerthan that of the substrate 102. For example, the material of thehalf-boat-shaped material layer 106 includes silicon nitride, and thehalf-boat-shaped material layer 106 is formed through a nitrogen atomimplantation process. Besides, a top surface 105 of the half-boat-shapedmaterial layer 106 is coplanar with the surface of the substrate 102. Abow portion 107 of the half-boat-shaped material layer 106 has aninclined sidewall 107 a, and an angle θ formed by the inclined sidewall107 a of the half-boat-shaped material layer 106 and the top surface 105of the same (or the surface of the substrate 102) is smaller than about30°. In addition, a laser enters from a stern portion 109 of thehalf-boat-shaped material layer 106.

The deep trench isolation structure 108 is disposed in the substrate 102within the first area 104 a and located at one side of the bow portion107 of the half-boat-shaped material layer 106. The depth of the deeptrench isolation structure 108 is in micro level. In an embodiment, thedepth of the deep trench isolation structure 108 may be about 2 μm.Besides, the deep trench isolation structure 108 and thehalf-boat-shaped material layer 106 may be kept a distance apart (asshown in FIG. 1) or directly adjacent to each other (as shown in FIG. 3)according to the design requirement.

The optical waveguide 110 is disposed on the substrate 102 within thefirst area 104 a and overlaps a portion of the deep trench isolationstructure 108 and at least a portion of the half-boat-shaped materiallayer 106. In an embodiment, the optical waveguide 110 overlaps aportion of the half-boat-shaped material layer 106, as shown in FIG. 1.In another embodiment, the optical waveguide 110 overlaps the entirehalf-boat-shaped material layer 106, as shown in FIG. 3. The material ofthe optical waveguide 110 includes polysilicon, amorphous silicon, orsingle crystal silicon. In an embodiment, an insulation layer 112 may bedisposed between the optical waveguide 110 and the substrate 102,wherein the material of the insulation layer 112 may be silicon oxide.

Additionally, the optoelectronic device 100 further includes a MOSdevice 130 disposed within the second area 104 b. The MOS device 130includes an insulation layer 120, a gate 122, a spacer 124, andsource/drain regions 126. The gate 122 is disposed on the substrate 102.The insulation layer 120 is disposed between the gate 122 and thesubstrate 102. The spacer 124 is disposed on a sidewall of the gate 122.Each of the source/drain region 126 includes a lightly doped region 125and a heavily doped region 127, and the source/drain regions 126 aredisposed in the substrate 102 beside the spacer 124. It is for sure thatin the second area 104 b, the MOS device 130 may further include a metalsilicide layer and an interconnection structure thereon such as acontact hole, a via, an interlayer dielectric layer, and a metal layer,etc. These elements are well known to those having ordinary knowledge inthe art therefore will not be described herein.

The optoelectronic device 100 further includes a dielectric layer 132.The dielectric layer 132 is disposed on the substrate 102 and covers theoptical waveguide 110 and the MOS device 130. The material of thedielectric layer 132 may be silicon oxide or silicon nitride.

It should be noted that because the material of the dielectric layer 132is silicon oxide and the material of the half-boat-shaped material layer106 is SiO_(x), the refractive indexes of the dielectric layer 132 andthe half-boat-shaped material layer 106 are both lower than therefractive index of the substrate 102. Accordingly, after the laserenters from the stern portion 109 of the half-boat-shaped material layer106, the laser is totally internally reflected by the dielectric layer132 and the half-boat-shaped material layer 106 and then enters theoptical waveguide 110. Namely, the dielectric layer 132, thehalf-boat-shaped material layer 106, and the substrate 102 therebetweenform a coupler 118 such that light can be effectively focused and ledinto the optical waveguide 110. Herein even though the insulation layer112 is disposed between the optical waveguide 110 and the substrate 102,the path of the laser entering the optical waveguide 110 won't bechanged because the insulation layer 112 is very thin (less than 100 Å).

After the optical waveguide 110 and the coupler 118 within the firstarea 104 a and the MOS device 130 within the second area 104 b areformed in a single chip, a laser 140 is coupled to the stern portion 109of the half-boat-shaped material layer 106 through an optical fiber 138by performing a packaging process, so as to complete the packaging ofthe optoelectronic device 100. FIG. 4 is a simplified schematic top viewillustrating the packaging of the optoelectronic device 100.

In the embodiment described above, a MOS device is formed within thesecond area. However, the present invention is not limited thereto. Itshould be understood by those having ordinary knowledge in the art thatother electronic devices (for example, resistors, capacitors, orfield-effect transistors (FETs), etc) may also be formed within thesecond area.

Below, a method of forming an optoelectronic device provided by thepresent invention will be described. FIGS. 5A-5D are schematiccross-sectional views illustrating the method of forming anoptoelectronic device according to a first embodiment of the presentinvention.

First, referring to FIG. 5A, a substrate 102 is provided. The substrate102 may be a bulk-Si substrate and has a first area 104 a and a secondarea 104 b, wherein the first area 104 a is used for forming opticaldevices, such as an optical waveguide 110 and a coupler 118, and thesecond area 104 b is used for forming electronic devices, such as a MOSdevice 130. Then, a plurality of ion implantation processes is performedon the substrate 102 to form a plurality of step-shaped ion implantedregions 106 a to 106 e in the substrate 102 within the first area 104 a.FIG. 6 is a schematic three-dimensional view of the ion implantedregions 106 a to 106 e, wherein the ion implanted regions 106 a to 106 deach present a ring shape so as to form the top and side surfaces of ahalf-boat-shaped material layer 106, and the ion implanted region 106 epresents a sheet-like shape so as to form the bottom surface of thehalf-boat-shaped material layer 106. In an embodiment, each of the ionimplantation processes may be an O⁺ ion implantation process. Theimplantation dosage of an O⁺ ion implantation process may be about10¹⁴-10²¹ atoms per cubic centimeter, and the implantation energythereof can be adjusted according to the implantation depth.

In the embodiment described above, the ion implanted regions 106 a to106 e are separated from each other, and the distance between two of theion implanted regions 106 a to 106 e should allow the diffusion areasthereof overlap each other after the ion implanted regions 106 a to 106e are annealed. It is for sure that the ion implanted regions 106 a to106 e may also be kept directly adjacent to each other. In addition, thenumber, sequence, dosage, and energy of the ion implantation processesare not limited in the present embodiment and can all be adjustedaccording to the design requirement. Moreover, the implanted ions arenot limited to O⁺, and it is within the scope of the present inventionas long as the refractive index of the annealed half-boat-shapedmaterial layer 106 is lower than the refractive index of the substrate102. For example, the material of the half-boat-shaped material layer106 includes silicon nitride, and the half-boat-shaped material layer106 is formed through a nitrogen atom implantation process.

Thereafter, referring to FIG. 5B, an annealing process is optionallyperformed to diffuse the ion implanted regions 106 a to 106 e, so as toform the half-boat-shaped material layer 106. The annealing process canbe omitted, and the diffusion of the ion implanted regions 106 a to 106e can be completed through the subsequent high-temperature process whenthe shallow trench isolation structure 101 and the deep trench isolationstructure 108 are formed. FIG. 2 is a schematic three-dimensional viewof the half-boat-shaped material layer 106. The material of thehalf-boat-shaped material layer 106 may be SiO_(x). Besides, a topsurface 105 of the half-boat-shaped material layer 106 is coplanar withthe surface of the substrate 102. A bow portion 107 of thehalf-boat-shaped material layer 106 has an inclined sidewall 107 a, andthe angle θ formed by the inclined sidewall 107 a of thehalf-boat-shaped material layer 106 and the top surface 105 of the same(or the surface of the substrate 102) is smaller than about 30°.

Next, at least one shallow trench isolation structure 101 is formed inthe substrate 102. The first area 104 a and the second area 104 b may beseparated by the shallow trench isolation structure 101. The shallowtrench isolation structure 101 may be formed through following steps.First, a mask layer (not shown) and a patterned photoresist layer (notshown) are sequentially formed on the substrate 102. Then, a portion ofthe mask layer is removed by using the patterned photoresist layer as amask, so as to form patterned mask layer. After that, a portion of thesubstrate 102 is removed by using the patterned mask layer as a mask, soas to form a shallow trench 113. Next, an isolation layer 115 is filledin the shallow trench 113 to form a shallow trench isolation structure101. After that, the patterned mask layer is removed.

Thereafter, a deep trench isolation structure 108 is formed in thesubstrate 102 within the first area 104 a, and the deep trench isolationstructure 108 is formed at one side of the bow portion 107 of thehalf-boat-shaped material layer 106. The deep trench isolation structure108 is formed through following steps. First, a mask layer (not shown)and a patterned photoresist layer (not shown) are sequentially formed onthe substrate 102. Then, a portion of the mask layer is removed by usingthe patterned photoresist layer as a mask, so as to form a patternedmask layer. Next, a portion of the substrate 102 is removed by using thepatterned mask layer as a mask, so as to form a deep trench 117. Afterthat, an isolation layer 119 is filled in the deep trench 117 to formthe deep trench isolation structure 108. Next, the patterned mask layeris removed. The depth of the deep trench isolation structure 108 is inmicron level. In an embodiment, the depth of the deep trench isolationstructure 108 may be about 2 μm. In the present embodiment, the deeptrench isolation structure 108 and the half-boat-shaped material layer106 are kept a distance apart. However, the present invention is notlimited thereto, and in another embodiment, the deep trench isolationstructure 108 and the half-boat-shaped material layer 106 may also bedesigned directly adjacent to each other, as shown in FIG. 3.

The sequence of forming the shallow trench isolation structure 101, thedeep trench isolation structure 108 and the half-boat-shaped materiallayer 106 can be adjusted upon the process requirements. For example,the shallow trench isolation structure 101 and the deep trench isolationstructure 108 are formed before forming the half-boat-shaped materiallayer 106. Further, the sequence of forming the shallow trench isolationstructure 101 and the deep trench isolation structure 108 can beadjusted as needed. Besides, the annealing process of thehalf-boat-shaped material layer 106 can be performed before forming theshallow trench isolation structure 101 and the deep trench isolationstructure 108. Alternatively, the annealing process can be omitted, andthe diffusion of the ion implanted regions 106 a to 106 e can becompleted through the subsequent process when the well region and thesource/drain regions are annealed.

Next, referring to FIG. 5C, an insulation material layer 119, aconductive layer 121, and a patterned photoresist layer 123 aresequentially formed on the substrate 102. The material of the insulationmaterial layer 119 may be silicon oxide, and the insulation materiallayer 119 may be formed through thermal oxidation or a patterning methodby using a mask. The material of the conductive layer 121 may bepolysilicon, and the conductive layer 121 may be formed through chemicalvapour deposition (CVD).

Next, referring to FIG. 5D, the conductive layer 121 and the insulationmaterial layer 119 are sequentially etched by using the patternedphotoresist layer 123 as a mask, so as to form an insulation layer 112and an optical waveguide 110 on the substrate 102 within the first area104 a and an insulation layer 120 and a gate 122 on the substrate 102within the second area 104 b. The optical waveguide 110 overlaps aportion of the deep trench isolation structure 108 and at least aportion of the half-boat-shaped material layer 106. In the presentembodiment, the optical waveguide 110 overlaps a portion of thehalf-boat-shaped material layer 106. However, the present invention isnot limited thereto, and in another embodiment, the optical waveguide110 may also overlap the entire half-boat-shaped material layer 106, asshown in FIG. 3. Thereafter, the patterned photoresist layer 123 isremoved and the fabrication of the optical waveguide 110 and the coupler118 within the first area 104 a is completed.

After that, referring to FIG. 5D again, the process is continued tocomplete the fabrication of the MOS device 130 within the second area104 b. Lightly doped region 125 are formed in the substrate 102 besidethe gate 122. A spacer 124 is formed on a sidewall of the gate 122.Heavily doped regions 127 are formed in the substrate 102 beside thespacer 124. An annealing process is performed to the doped regions toactivate the dopants therein. The lightly doped regions 125 and theheavily doped regions 127 form source/drain regions 126. A dielectriclayer 132 is formed on the substrate 102 to cover the MOS device 130 andthe optical waveguide 110. The spacer 124, the source/drain regions 126,the dielectric layer 132, and other elements that are not shown here(for example, the metal silicide layer, the contact hole, the via, theinterlayer dielectric layer, and the metal layer, etc) are all wellknown to those having ordinary knowledge in the art and accordingly thematerials and formation techniques thereof will not be described herein.By now, the optoelectronic device 100 in the present invention iscompleted, wherein the first area 104 a contains the optical waveguide110 and the coupler 118, the second area 104 b contains the MOS device130, and a laser enters the optical waveguide 110 through the coupler118 to carry out subsequent processes.

In the first embodiment, the gate 120 of the MOS device 130 is formedsimultaneously when the optical waveguide 110 is formed. However, thepresent invention is not limited thereto, and the MOS device 130 mayalso be formed after the optical waveguide 110 is formed, as describedin the second embodiment. Below, the difference between the firstembodiment and the second embodiment will be described, and thesimilarity are not iterated herein. FIGS. 7A-7C are schematiccross-sectional views illustrating a method of forming an optoelectronicdevice according to a second embodiment of the present invention.

First, an intermediate structure as shown in FIG. 5B is provided. Then,referring to FIG. 7A, an insulation material layer 119, an conductivelayer 121, and a patterned photoresist layer 125 are sequentially formedon the substrate 102. The material of the insulation material layer 119may be silicon oxide, and the insulation material layer 119 may beformed through thermal oxidation. The material of the conductive layer121 may be polysilicon, amorphous silicon, or single crystal silicon,and the conductive layer 121 may be formed through CVD.

Next, referring to FIG. 7B, the conductive layer 121 and the insulationmaterial layer 119 are sequentially etched by using the patternedphotoresist layer 125 as a mask, so as to form the insulation layer 112and the optical waveguide 110 on the substrate 102 within the first area104 a. The optical waveguide 110 overlaps a portion of the deep trenchisolation structure 108 and at least a portion of the half-boat-shapedmaterial layer 106. Finally, the patterned photoresist layer 125 isremoved so that the fabrication of the optical waveguide 110 and thecoupler 118 within the first area 104 b is completed.

Thereafter, referring to FIG. 7C, the MOS device 130 is formed withinthe second area 104 b. An insulation layer 120 and a gate 122 aresequentially formed on the substrate 102. Lightly doped region 125 areformed in the substrate 102 beside the gate 122. A spacer 124 is formedon a sidewall of the gate 122. Heavily doped region 127 are formed inthe substrate 102 beside the spacer 124. The lightly doped regions 125and the heavily doped regions 127 form source/drain regions 126. Adielectric layer 132 is formed on the substrate 102 to cover the MOSdevice 130 and the optical waveguide 110. By now, the optoelectronicdevice 100 in the present invention is completed.

As described above, in an optoelectronic device provided by the presentinvention, an optical waveguide, a coupler, and a MOS device areeffectively integrated into a single chip so that less surface area istaken and the system is simplified. In addition, in the method offorming an optoelectronic device provided by the present invention, anoptical waveguide, a coupler, and a MOS device are formed on a bulk-Sisubstrate by using the existing semiconductor equipments. Namely, themethod of forming an optoelectronic device provided by the presentinvention can avoid fine tuning the modeling of the MOS device formed ona silicon-on-insulator (SOI) substrate, so that the fabrication cost ofthe optoelectronic device is greatly reduced and the competitivenessthereof is improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. An optoelectronic device, comprising: asubstrate, having a first area; a half-boat-shaped material layer,disposed in the substrate within the first area, wherein a refractiveindex of the half-boat-shaped material layer is lower than a refractiveindex of the substrate, and a top surface of the half-boat-shapedmaterial layer is coplanar with a surface of the substrate; a deeptrench isolation structure, disposed in the substrate within the firstarea, and located at one side of a bow portion of the half-boat-shapedmaterial layer; and an optical waveguide, disposed on the substratewithin the first area, and overlapping a portion of the deep trenchisolation structure and at least a portion of the half-boat-shapedmaterial layer.
 2. The optoelectronic device according to claim 1,wherein the substrate comprises a bulk-Si substrate.
 3. Theoptoelectronic device according to claim 1, wherein a material of thehalf-boat-shaped material layer comprises SiO_(x).
 4. The optoelectronicdevice according to claim 1, wherein a material of the optical waveguidecomprises polysilicon, amorphous silicon, or single crystal silicon. 5.The optoelectronic device according to claim 1, wherein a depth of thedeep trench isolation structure is in micron level.
 6. Theoptoelectronic device according to claim 1, wherein the deep trenchisolation structure and the half-boat-shaped material layer are kept adistance apart or directly adjacent to each other.
 7. The optoelectronicdevice according to claim 1, wherein a laser is coupled to a sternportion of the half-boat-shaped material layer through an optical fiber.8. The optoelectronic device according to claim 1, wherein the substratefurther comprises a second area, and the first area and the second areaare separated from each other by a shallow trench isolation structure.9. The optoelectronic device according to claim 8, further comprising ametal-oxide-semiconductor (MOS) device disposed within the second area.10. A method of forming an optoelectronic device, comprising: providinga substrate, wherein the substrate has a first area; forming ahalf-boat-shaped material layer within the first area, wherein arefractive index of the half-boat-shaped material layer is lower than arefractive index of the substrate, and a top surface of thehalf-boat-shaped material layer is coplanar with a surface of thesubstrate; forming a deep trench isolation structure in the substratewithin the first area, wherein the deep trench isolation structure isformed at one side of a bow portion of the half-boat-shaped materiallayer; and forming an optical waveguide on the substrate within thefirst area, wherein the optical waveguide overlaps a portion of the deeptrench isolation structure and at least a portion of thehalf-boat-shaped material layer.
 11. The method according to claim 10,wherein the step of forming the half-boat-shaped material layercomprises performing a plurality of ion implantation processes on thesubstrate to form a plurality of step-shaped ion implanted regions inthe substrate within the first area.
 12. The method according to claim11, wherein each of the ion implantation processes comprises an O⁺ ionimplantation process.
 13. The method according to claim 11, wherein animplantation dosage of each of the ion implantation processes is about10¹⁴-10²¹ atoms per cubic centimeter.
 14. The method according to claim11, wherein the step of forming the half-boat-shaped material layerfurther comprises performing an annealing process to diffuse the ionimplanted regions, so as to form the half-boat-shaped material layer.15. The method according to claim 10, wherein the substrate comprises abulk-Si substrate.
 16. The method according to claim 10, wherein amaterial of the optical waveguide comprises polysilicon, amorphoussilicon, or single crystal silicon.
 17. The method according to claim10, wherein a depth of the deep trench isolation structure is in micronlevel.
 18. The method according to claim 10, wherein the deep trenchisolation structure and the half-boat-shaped material layer are kept adistance apart or directly adjacent to each other.
 19. The methodaccording to claim 10, wherein the substrate further comprises a secondarea, and the first area and the second area are separated from eachother by a shallow trench isolation structure.
 20. The method accordingto claim 19, further comprising forming a MOS device within the secondarea.
 21. The method according to claim 20, wherein a gate of the MOSdevice is simultaneously formed during the step of forming the opticalwaveguide.
 22. The method according to claim 20, wherein the MOS deviceis formed after the optical waveguide is formed.